PROJECT ABSTRACT The proposed K01 award will provide Dr. Martinez with the support necessary to achieve her immediate training goals: 1) to gain expertise in pediatric sleep science and measurement to complement her strong training in nutrition and physical activity, 2) to increase understanding of child growth and development as it relates to energy balance, and 3) to advance her skills in research design to plan an RCT. This training will provide her with the skills necessary to establish her independent research program. To achieve these goals, Dr. Martinez has assembled a team of mentors with relevant expertise to fill the gaps of her research experience. Her mentoring team includes: Dr. Ronald Dahl, with expertise in pediatric sleep; Dr. Sheila Gahagan, with expertise in child growth and development; Dr. Jeanne Tschann, with expertise in Latino family dynamics, study implementation, recruitment and retention specifically in Latino families; Dr. Nancy Butte, with expertise in pediatric obesity and metabolism; and Dr. Patricia Crawford, with expertise in community nutrition and clinical trials and a track record of excellent mentorship. With this K01 award, Dr. Martinez will achieve her long-term goal to become an independent investigator conducting energy-balance related research on how to reduce chronic disease in underserved Latino children. Individuals of Mexican descent comprise the largest proportion of the Latino population in the United States and they suffer high rates of obesity. An improved understanding of the underlying behavioral mechanisms by which short sleep duration may impact obesity among Mexican American children is critical to prevent and/or reduce obesity and chronic disease in this population. Dr. Martinez's research will focus on: behavioral mechanisms (i.e., diet and physical activity) that link sleep duration to obesity (Aim 1). These relationships will be examined in an existing data set of Mexican American 8-10-year-olds (n=323). For Aim 2 and Aim 3, data will be collected in a new sample of Mexican American 8-10-year-olds to examine: 1) contextual factors (i.e., bedtime routines, sleep hygiene, familism) that may impact sleep (Aim 2); and 2) the impact of prior night's sleep duration on diet and physical activity the subsequent day (Aim 3). This research will be used to plan a randomized control intervention to promote optimal sleep, healthy eating and physical activity among Mexican American children, to be proposed in a R34 grant application before the end of the K01 award.